Autumn Purple is a cultivar of Fraxinus americana, commonly known as the white ash tree. White ash is a deciduous tree, native to the majority of North America. The Autumn Purple cultivar was first introduced in 1956 and is now prized for its beautiful fall foliage, which often turns earlier in the season and lasts longer than most other trees that show fall color.
The bark is brownish-gray and smooth when young, eventually becoming rough and deeply furrowed. The leaves of Autumn Purple white ash are compound, with a long leaf stem and five to nine leaflets. The leaflets are opposite each other down the length of the stem, with a single leaflet on the end. They are lance-shaped, green, and approximately two to four inches long. In the fall, the leaves turn deep red, maroon or purple in color.
The tree's flowers, which appear in spring, are little, green and inconspicuous. Autumn Purple white ash is an exclusively male variety and does not produce seeds.
Growing fast, Autumn Purple can gain over two feet of new growth per year. The roots are shallow and easily seen on the surface of the ground, under the canopy of the tree and can lift sidewalks and driveways, if planted too closely. Autumn Purple grows well in hardiness zones 3B through 9A.
The tree usually grows from a single leading trunk with large branches reaching outward and upward. It is a tall upright plant that can grow to 50 feet tall and just as wide. The tree is pyramid-shaped with a round top, when young, eventually rounding even more to an oval shape as it matures. The canopy is symmetrical with a regular outline, relatively dense and medium in texture.
Autumn Purple white ash prefers full sun, although it will tolerate partial shade. The tree is adaptable to a wide variety of soils and will thrive in clay, loam or sand, as long as the soil is well-draining. Moderately drought tolerant, the plant can also handle occasionally wet conditions. Autumn Purple requires little pruning to develop well. It is prone to attack from ash borers and boring insects common to ash trees.
Autumn Purple white ash works well as a shade tree and is popular for landscaping medium-sized spaces. It is often used in plantings around parking lots, in median strips and to line streets and highways. Autumn Purple can also be used in residential settings as a shade and yard tree.